Lecture 4: Information Networks (40 slides)

Lecture 4: Information Networks (40 slides) Information technology Lecturer: Prof. Anatoly Sachenko

Lecture Overview • LAN and WAN • Topologies and Architectures of Computer Networks • Intranet and Extranet • The Internet • The Telephone Network in Computing • Data Transfer • Modem

LAN and WAN • A local area network (LAN) is a computer network covering a small geographic area, like a home, office, or group of buildings • It allows to share the memory, printers, applications and files across a network • It extends for a few km • The defining characteristics of LAN, in contrast to Wide Area Network (WAN), include: • their much higher data transfer rates • smaller geographic range

WAN • Wide Area Network (WAN) is a computer network that covers a broad area (i.e., any network whose communications links cross metropolitan, regional, or national boundaries) • The largest and most well-known example of a WAN is the Internet • WANsare used to connect LANs and other types of networks together (see next slide) • so that users and computers in one location can communicate with users and computers in other locations • Many WANs are built for one particular organization and are private

LAN and WAN Illustrations

LAN and WAN – Client/Server • A client is an application or system that accesses a (remote) service on another computer system known as a server by way of a network • A server is an application or device that performs services for connected clients as part of a client-server architecture • A server computer (often called server for short) is a computer system that has been designated for running a specific server application • Client-server is a computing architecture which separates a client from a server, and is almost always implemented over a computer network • Each client or server connected to a network can also be referred to as a node (continued on the next slide)

LAN and WAN - Client/Server (continued) • The most basic type of client-server architecture employs only two types of nodes: clients and servers • This type of architecture is sometimes referred to as two-tier • It allows devices to share files and resources • Protocol is a convention or standard that controls or enables the connection, communication, and data transfer between two computing endpoints • In its simplest form, a protocol can be defined as the rules governing the syntax, semantics, and synchronization of communication

LAN and WAN – Group Working • LAN and WAN have applications, which use client-server technology and orient for group working of network users • Printer sharing enable network users to use network printer, which is connected to the network in direct way or by means of server computer • File sharing enable to access and transfer files between computers of network • Application sharing is an element of remote access that enables network users to access a shared application or document from their respective computers simultaneously in real time

Topologies of Computer Networks • Topology - logical and physical methods of computers connection, cables and other components, on the whole constituent network • A topology characterises networks properties, not depending on their sizes Star Cellular Linear Ring Treelike

Architectures of Computer Networks – Ethernet and Token Ring • Ethernetis a broadcast network • It means that all stations can adopt all reports • Its topology is linear • Its data rate is 10 or 100 Mbit/s • It’s a most popular network at present • Token Ringis a ring network • Its principle of data communication is based on feature, that every site of ring expects arrival of some short unique bits sequence— marker, — from a contiguous previous site • Data rate 4 or 16 Mbit/s • It’s implemented and used by IBM

Architectures of Computer Networks - FDDI • FDDI (Fiber Distributed Data Interface) is network architecture of high speed data communication on fiber lines • Its transmission speed— 100 Mbit/s • A topology is a double ring or mixed (with including star-shaped or treelike subnet) • A maximal amount of the stations is in a network — 1000 • It has a vulnerable design and expensive cost of equipment • It’s used for a long distance communication, or local application providing data transfer of high speed

Architectures of Computer Networks – Wireless Networks • Wireless networks are used wherein the gasket of cables is laboured, inadvisable or simply impossible • If network will be implemented through radio-adapters, and using as data passing environment radio waves, such network will be implemented according to the topology “One connects to all” and capable of working at distance 50–200 m • Access point - device for connecting between wireless and cable parts of network • It is possible to use an ordinary computer two adapters of networks are set in which — wireless and cable

Architectures of Computer Networks – Wireless Networks (continued) • Other important application of wireless networks domain is connection organisation between the remote segments of local networks in default data communication infrastructure (general access cable networks, high-quality public-call lines and other) • In this case for aiming of wireless bridges between two remote segments radio-bridges are used with by aerial of the directed type

Intranet - Definitions • An Intranet is a network inside an organization that uses Internet technologies to provide an Internet-like environment within the enterprise for information sharing, communications, collaboration, and the support of business processes • HTTP and other Internet protocols are commonly used as well, such as FTP • An Intranet is protected by security measures such as passwords, encryption, and firewalls, and thus can be accessed by authorized users through the Internet (continued on the next slide)

Intranet - Illustration

Extranet • An extranet is a private network • An extranet can be viewed as part of a company's Intranet that is extended to users outside the company • It uses Internet protocols, network connectivity, and possibly the public telecommunication system to securely share part of an organization's information or operations with suppliers, vendors, partners, customers or other businesses

Extranet (continued)

The Internet • The Internet is a worldwide, publicly accessible series of interconnected computer networks that transmit data by packet switching using the standard Internet Protocol (IP) • It is a "network of networks" that consists of millions of smaller domestic, academic, business, and government networks, which together carry various information and services • Such as electronic mail, online chat, file transfer, and the interlinked Web pages and other documents of the World Wide Web (continued on the next slide)

The Internet Protocols • Aside from the complex physical connections that make up its infrastructure, the Internet is facilitated by bi- or multi-lateral commercial contracts and by technical specifications or protocols that describe how to exchange data over the network • Indeed, the Internet is essentially defined by its interconnections and routing policies • There are three layers of Internet protocols: • At the lower level is IP(Internet Protocol), which defines the datagrams or packets that carry blocks of data from one node to another (continued on the next slide)

The Internet Protocols (continued) • TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) exist at the next layer up; these are the protocols by which data is transmitted • TCP makes a virtual 'connection', which gives some level of guarantee of reliability. • UDP is a best-effort, connectionless transport, in which data packets that are lost in transit will not be re-sent • The application protocolssit on top of TCP and UDP • It defines the specific messages and data formats sent and understood by the applications running at each end of the communication • Examples of these protocols are HTTP (Hypertext Transfer Protocol), FTP, and SMTP (Simple Mail Transfer Protocol)

The Internet Uses • The Internet has many common uses • E-mail. The concept of sending electronic text messages between parties in a way analogous to mailing letters or predates the creation of the Internet • Remote access. The Internet allows computer users to connect to other computers and information stores easily, wherever they may be across the world • File sharing. • A computer file can be e-mailed to customers, colleagues and friends as an attachment (continued on the next slide)

The Internet Uses (continued) • It can be uploaded to a Web site or FTP server for easy download by others • It can be put into a "shared location" or onto a file server for instant use by colleagues • The load of bulk downloads to many users can be eased by the use of "mirror" servers or peer-to-peer networks • Streaming media. Many existing radio and television broadcasters provide Internet 'feeds' of their live audio and video streams (for example, the BBC and Rush Limbaugh) (continued on the next slide)

The Internet Uses (continued) • They may also allow time-shift viewing or listening such as Preview, Classic Clips and Listen Again features • An Internet-connected device, such as a computer or something more specific, can be used to access on-line media in much the same way as was previously possible only with a television or radio receiver • Voice telephony (VoIP). Voice over Internet Protocol, also called VoIP , IP Telephony, Internet telephony, is the routing of voice conversations over the Internet or through any other IP-based network

The Internet - World Wide Web • The World Wide Web (commonly shortened to the Web) is a system of interlinked, hypertext documents accessed via the Internet • With a web browser, a user views web pages that may contain text, images, videos, and other multimedia and navigates between them using hyperlinks • The World Wide Web was created in 1989 by Sir Tim Berners-Lee and Sir Sam Walker from the United Kingdom, and Robert Cailliau from Belgium, working at CERN in Geneva, Switzerland (continued on the next slide)

World Wide Web (continued) • Viewing a web page on the World Wide Web normally begins either by typing the URL (Uniform Resource Locator) of the page into a web browser, or by following a hypertext link to that page or resource • The web browser then begins a series of communications, behind the scenes, in order to fetch and display it

World Wide Web Illustration

The Telephone Network in Computing - Public Switched Telephone Network • The public switched telephone network (PSTN) is the network of the world's public circuit-switched phone networks, in much the same way that the Internet is the network of the world's public IP-based packet-switched networks • Originally a network of fixed-line analog phone systems, the PSTN is now almost entirely digital, and now includes mobile as well as fixed phones • The PSTN is largely governed by technical standards created by the ITU-T (International Telecommunication Union) • It uses E.163/E.164 addresses (known more commonly as phone numbers) for addressing

The Telephone Network in Computing- ISDN • Integrated Services Digital Network (ISDN) is a circuit-switched telephone network system • It’s designed to allow digital transmission of voice and data over ordinary telephone copper wires, resulting in better quality and higher data speeds than are available with analog • More broadly, ISDN is a set of protocols for establishing and breaking circuit switched connections, and for advanced call features for the user • It was invented by Prof. Jaxin Hall of Sussex, UK in the late 1980's (continued on the next slide)

The Telephone Network in Computing- ISDN (continued) • In a videoconference, ISDN provides simultaneous voice, video, and text transmission between individual desktop videoconferencing systems and group (room) videoconferencing systems • The purpose of the ISDN is to provide fully integrated digital services to the user • These services fall under three categories: • bearer services, supplementary services and teleservices

The Telephone Network in Computing – ISDN Illustration

The Telephone Network in Computing - ADSL • Asymmetric Digital Subscriber Line (ADSL) is a form of data communications technology that enables faster data transmission over copper phone lines than a conventional voiceband modem can provide • It does this by utilizing frequencies that are not used by a voice telephone call • A splitter allows a single phone connection to be used for both ADSL service and voice calls at the same time • Because phone lines vary in quality it can be used generally over short distances only • It’s typically less than 5 km

Data Transfer- Analog and Discrete Signals • An analog or analoguesignal is any time continuous signal where some time varying feature of the signal is a representation of some other time varying quantity • A discrete signal or discrete-time signal is a time series, perhaps a signal that has been sampled from a continuous-time signal • Unlike a continuous-time signal, a discrete-time signal is not a function of a continuous-time argument • It’s is a sequence of quantities and each value in the sequence is called a sample

Data Transfer – Digital Signals • A digital signal is a discrete-time signal that takes on only a discrete set of values • It typically derives from a discrete signal that has been quantized • Quantization is the process of approximating a continuous range of values by a relatively-small set of discrete symbols or integer values • Common practical digital signals are represented as • 8-bit (256 levels), 16-bit (65,536 levels), 32-bit (4,3 billion levels), and so on

Data Transfer Rate • Data transfer rate or just transfer rate is the average number of bits, characters, or blocks per unit time passing between equipment in a data transmission system • Bitrate (sometimes written bit rate, data rate) is the number of bits that are conveyed or processed per unit of time • The bit rate is quantified using the 'bit per second' (bit/s or bps) unit, often in conjunction with a SI prefix such as kilo- (kbit/s or kbps), mega- (Mbit/s or Mbps), giga- (Gbit/s or Gbps) or tera- (Tbit/s or Tbps)

Data Transfer - Modem • Modem (from modulate and demodulate) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information • The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data • Modems can be used over any means of transmitting analog signals, from driven diodes to radio (continued on the next slide)

ADSL Modem • A cable modem is a type of modem that provides access to a data signal sent over the cable television infrastructure. Cable modems are primarily used to deliver broadband Internet access, taking advantage of unused bandwidth on a cable television network • ADSL modem or DSL modem is a device used to connect a single computer or router to a DSL phone line, in order to use an ADSL service • Some ADSL modems also manage the connection and sharing of the ADSL service with a group of machines: in this case, the unit is termed a DSL router or residential gateway (continued on the next slide)

ADSL Modem (continued) • Asymmetric digital subscriber line transceiver or ATU-R, as the telephone companies call it, is a functional block inside every ADSL modem which actually performs modulation, demodulation and framing • Typical user interfaces are Ethernet and USB • Although an ADSL modem working as a bridge doesn't need an IP address, it may have one assigned for management purposes • ADSL modem is depicted on the next slide

ADSL Modem Sample

References • European Computer Driven Licence, Syllabus version 4.0, 2006. • Lecture Notes. Fundamentals of Informatics (e-version). Based on a book by L.Z.Shaucukova. Informatics (in Russian).Moscow, 2002. – 420 p. (translated and edited by Anatoly Sachenko). • William Stallings. Computer Organization and Architecture: Designing for Performance (6th edition). Prentice Hall , 2002, 750 p. • Tucker (Editor-in-Chief), R. Cupper, F.P. Deek, and R. Noonan (Editorial advisors), Computer Science Handbook, Second edition, CRC Press, 2004, 2752 p. • Hysa B., Piekoszewska B., Rakowiecka K., Sobota M., Sołtysik-Piorunkiewicz A., Zdonek D., Zdonek I., : Laboratorium z podstaw informatyki w zarządzaniu. Część II. Wprowadzenie do MS Windows. MS Word. Wydawnictwo PŚ. Gliwice 2003. Skrypt nr 2324.

References (continued) • Kowalczyk G.: Word 2000 PL. Ćwiczenia praktyczne. Helion, Gliwice 2000. • J. Glenn Brookshear. Computer science an overview, Sixth edition, Addison Wesley, 2001, 688 p. • Brookshear J.G.: Informatyka w ogólnym zarysie, Wydawnictwo WNT, Warszawa 2003. • http://www.roz6.polsl.pl/asachenko/sutaa.html

Lecture 4: Information Networks (40 slides)